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這篇文章主要介紹“如何擴展現(xiàn)有類、結(jié)構(gòu)體、枚舉”,在日常操作中,相信很多人在如何擴展現(xiàn)有類、結(jié)構(gòu)體、枚舉問題上存在疑惑,小編查閱了各式資料,整理出簡單好用的操作方法,希望對大家解答”如何擴展現(xiàn)有類、結(jié)構(gòu)體、枚舉”的疑惑有所幫助!接下來,請跟著小編一起來學(xué)習吧!
//擴展 Double 計算屬性 extension Double { var km: Double { return self * 1_000.0 } var m: Double { return self } var cm: Double { return self / 100.0 } var mm: Double { return self / 1_000.0 } var ft: Double { return self / 3.28084 } } let oneInch = 25.4.mm print("One inch is \(oneInch) meters") //One inch is 0.0254 meters let threeFeet = 3.ft print("Three feet is \(threeFeet) meters") //Three feet is 0.914399970739201 meters
//擴展初始化器 struct Rect{ var x = 0.0, y = 0.0 var width = 0.0, height = 0.0 } extension Rect { init(pos: [Double], size: [Double]) { self.init(x: pos[0], y: pos[1], width: size[0], height: size[1]) } } let r = Rect(pos: [0.0, 0.0], size: [4.0, 4.0])
//擴展方法 extension Int { func repeatTalk(talk: () -> Void) { for _ in 0..<self { talk() } } } 5.repeatTalk { print("Hi") } /* Hi Hi Hi Hi Hi */
//修改實例本身 mutating extension Int { mutating func square() { self = self * self } } var a = 5 a.square() print(a) //25
//擴展下標 extension Int { subscript(index: Int) -> Int { var base = 1 for _ in 0..<index { base *= 10 } return (self/base) % 10 } } print(12345678[0]) print(12345678[1]) print(12345678[2]) print(12345678[3]) print(12345678[4]) /* 8 7 6 5 4 */
//擴展內(nèi)嵌類型 extension Int { enum Kind { case negative, zero, positive } var kind: Kind { switch self { case 0: return .zero case let x where x > 0: return .positive default: return .negative } } } print(4.kind) //positive
到此,關(guān)于“如何擴展現(xiàn)有類、結(jié)構(gòu)體、枚舉”的學(xué)習就結(jié)束了,希望能夠解決大家的疑惑。理論與實踐的搭配能更好的幫助大家學(xué)習,快去試試吧!若想繼續(xù)學(xué)習更多相關(guān)知識,請繼續(xù)關(guān)注億速云網(wǎng)站,小編會繼續(xù)努力為大家?guī)砀鄬嵱玫奈恼拢?/p>
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